Combustion system analysis using laser-induced breakdown spectroscopy

Practical combustion systems are characterized by rapid fluctuations due to turbulence and unsteady operation. Real-time diagnostic and analysis methods must be both highly sensitive and capable of capturing significant amounts of information instantly. This talk describes the use of Laser-Induced Breakdown Spectroscopy (LIBS) for combustion system analysis, including the measurement of complete mixture fraction, inorganic species concentrations, and/or associations of individual elements in aerosol particulate matter, in a single measurement. Equivalence ratio measurements in engines, parameterized by ratios of observed C, O, and N emission lines, have been used to determine fluctuations in operation and ascertain performance. In laboratory diffusion flames similar measurements have been used to determine PDFs of turbulent mixing between air and fuel. In addition, the composition of particulate matter may be monitored, both trace species and major species. These multiple measurement modalities make LIBS attractive as a general, broadband diagnostic for combustion systems. Future directions and new applications will be addressed.